An influenza pandemic is a global outbreak of disease that occurs when a new influenza A virus appears in humans, causes serious illness and then spreads easily from person to person worldwide. Three major influenza pandemics swept the globe in the 20th century causing millions of deaths, and no one knows for sure when the next pandemic may strike.

What’s the difference between a pandemic and a seasonal outbreak of flu?

A pandemic is caused by a new influenza A virus that most people have never been exposed to, so everyone is susceptible. Pandemic strains also often cause more serious disease. Because of this, past flu pandemics have led to high levels of illness, death, social disruption and economic loss.

Seasonal outbreaks of flu are caused by strains of flu virus similar to those of past years. Some people may have built up immunity, and there is also a vaccine for each year’s flu season.

Flu pandemics are different from many of the threats for which public health and the health-care system are currently planning:

The pandemic will last much longer than most other emergency events and may include waves of flu activity separated by months (in 20th century pandemics, a second wave of flu activity occurred three to 12 months after the first wave).

The numbers of health-care workers and first responders available to work can be expected to be reduced as they will be at high risk of illness through exposure in the community and in health care settings, and some may have to miss work to care for ill family members. Resources in many locations could be limited because of how widespread a flu pandemic would be.

Click here to view the current status of seasonal influenza activity in the U.S.

When will the next influenza pandemic occur?

Three pandemics occurred in the 20th century, all of which spread around the world within one year of being detected. Of these, the pandemic of 1918-1919 was the most severe, with 50 million or more deaths worldwide.

No one can predict when a pandemic might occur, but many scientists believe it is only a matter of time before the next one arises. Experts from around the world are watching the current worldwide Swine Flu (H1N1) and H5N1 Avian (bird) Flu situations very closely. There is current speculation that the Swine Flu outbreaks that we are now seeing may be the start of the next influenza pandemic. With that in mind, EMS Agencies and Health Care Providers need to make certain that they are prepared to face the challenges that will likely be brought by a influenza pandemic.

Characteristics and Challenges of a Pandemic

Rapid Worldwide Spread

When a pandemic influenza virus emerges, its global spread is considered inevitable. Preparedness activities should assume that the entire world population would be susceptible. Countries might, through measures such as border closures and travel restrictions, delay arrival of the virus, but cannot stop it.

Health Care Systems Overloaded

Most people have little or no immunity to a pandemic virus. Infection and illness rates soar. A substantial percentage of the world’s population will require some form of medical care. Nations unlikely to have the staff, facilities, equipment and hospital beds needed to cope with large numbers of people who suddenly fall ill. Death rates are high, largely determined by four factors: the number of people who become infected, the virulence of the virus, the underlying characteristics and vulnerability of affected populations and the effectiveness of preventive measures. Past pandemics have spread globally in two and sometimes three waves.

Inadequate Medical Supplies

The need for vaccine is likely to outstrip supply. The need for antiviral drugs is also likely to be inadequate early in a pandemic. A pandemic can create a shortage of hospital beds, ventilators and other supplies. Surge capacity at non-traditional sites such as schools may be created to cope with demand Difficult decisions will need to be made regarding who gets antiviral drugs and vaccines.

Economic and Social Disruption

Travel bans, closings of schools and businesses and cancellations of events could have major impact on communities and citizens. Care for sick family members and fear of exposure can result in significant worker absenteeism.

The Potential Impact of Pandemic Influenza

If a new and severe strain of flu were to begin spreading across the globe, Virginia would not be spared from its impact. The severity of the next pandemic cannot be predicted, but modeling studies suggest that its effect in the United States could be severe.

In the absence of any control measures (vaccination or drugs), it has been estimated that in the United States a “medium–level” pandemic could cause:

Deaths: 89,000 to 207,000 Hospitalizations:314,000 and 734,000 Outpatient Visits: 18 to 42 million Number of Sick Persons: 20 to 47 million people

In Virginia, pandemic flu impact estimates include:

Deaths: 2,700 to 6,300 Hospitalizations:12,000 to 28,500 Outpatient Visits: 575,000 to 1.35 million 1.08 million to 2.52 million people becoming sick